HOW can I not get this?

5. [1pt] A sailboat tacking against the wind moves as follows: 2.8 km at 27° east of north, 4.7 km at 28° west of north, and 3.9 km at 28° east of north. The entire trip takes 4 h 25 min. What is the magnitude of the displacement of the sailboat at the end of the trip ?